Organosilicon materials such as organosilanes or organopolysiloxanes have been used as water repellents for porous substrates. They have been used as coatings on the porous substrate or as additives incorporated into the porous substrate, for example incorporated into a cementitious composition before it is set.
EP 811584 describes a granulated hydrophobing additive in cement. The granulated additive comprises an active organopolysiloxane component a water-soluble or water dispersible binder and water-soluble, water-insoluble or water dispersible carrier particles. The additive is readily dispersible in cementitious materials upon the addition of water due to the non-hydrophobic nature of the binder and carrier of the granules.
WO 2008/062018 describes a process for preparing a granulated hydrophobing additive for cementitious material in which an organosilicon component and a binder polymer are applied to a particulate carrier from aqueous emulsion. The granulated hydrophobic additive thus prepared provides a high initial hydrophobicity to cementitious materials to which it is applied and the hydrophobicity can last during a long period of time.
U.S. Pat. No. 6,268,423 describes building compositions containing hydrophobing powders comprising silica as support material and an organosilicon compound and optionally solvent and/or water and emulsifier.
US 2012/0101227 discloses aqueous suspensions of silicate shell microcapsules wherein a first portion of the silicate shell micro-capsules contain an organopolysiloxane having at least two alkenyl groups and a hydrosilylation catalyst as Part A of a curable siloxane composition, and a second portion of the silicate shell microcapsules contain an organohydrogensiloxane as Part B of the curable siloxane composition.
U.S. Pat. No. 6,251,313 discloses the preparation of microcapsules having shell walls of organopolysiloxane and a core material, where the shell walls are produced in situ by hydrolysis and polycondensation of organosilanes and/or their condensates having not more than 4 silicon atoms.
US 2004/0256748 relates to a process for preparing silica microcapsules and more particularly, to a process for preparing silica microcapsules comprising the steps of dissolving tetraethyl orthosilicate (TEOS) into an aqueous solution containing a hydrolysis catalyst to control a degree of hydrolysis and contribute hydrophilicity or lipophilicity, adding a core material and an appropriate amount of aminopropyltrialkoxysilane(APS) as a gelling agent into the solution, and emulsifying and dispersing the resulting solution to a solution having a polarity opposite to that of the core material to microcapsulate by coating the core material with silica shell via a sol-gel reaction.
EP 0811584 discloses a cementitious material in powder form comprising cement, also comprising sufficient of a granulated hydrophobing additive, which comprises from 5 to 15 parts by weight of an organopolysiloxane component, from 10 to 40 parts by weight of a water-soluble or water-dispersible binder and from 50 to 80 parts by weight of a carrier particle, to give from 0.01 to 5% by weight of the organosiloxane component based on the weight of the cement.
Although the granulated hydrophobing additives described above have been successful in rendering cementitious materials hydrophobic, the presence of the hydrophobic organosilicon component at the surface of the formed cementitious material impacts detrimentally the paintability of the cementitious material, that is the adhesion of a post-applied coating or paint.